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Flux Dynamics Of Mgb2 Superconductor By Ac Susceptibility Measurements, M. J. Qin, X. L. Wang, Saeid Soltanian, Hua-Kun Liu, S. X. Dou
Flux Dynamics Of Mgb2 Superconductor By Ac Susceptibility Measurements, M. J. Qin, X. L. Wang, Saeid Soltanian, Hua-Kun Liu, S. X. Dou
Shi Xue Dou
Flux dynamics of an MgB2 bulk sample have been studied by systematic measurements of the fundamental and third harmonic ac susceptibility. The irreversibility line Tirr(B) has been obtained by fitting the onset temperature Ton (I,B) of the third harmonics at different frequencies to Ton (f, B) = C(2~f)1/[(Z-1)V] +Jirr(B). The flux creep activation energy U(j, B,T) has been derived as U0[l- (T /TirrY]2(B / B0)-n (j / j0)-u, with n =1.33 and f1 =0.2. The steep decline of the activation energy as a function of the magnetic field U(B) oc B-1.33 leads to the steep drop in the critical current …
Suppression Of Ac (Hysteretic) Loss By Magnetic Shielding Of Mgb2/Fe Superconductors: The Pseudo-Meissner Effect, M. D. Sumption, E. Lee, E. W. Collings, X. L. Wang, S. X. Dou
Suppression Of Ac (Hysteretic) Loss By Magnetic Shielding Of Mgb2/Fe Superconductors: The Pseudo-Meissner Effect, M. D. Sumption, E. Lee, E. W. Collings, X. L. Wang, S. X. Dou
Shi Xue Dou
The M-H loops of MgB2 materials in bulk sintered form, as well as for PIT wire and tape MgB2/Fe monofilamentary composites, have been measured at various temperatures. The influence of Fe on the M-H loops of the tape and wire are discussed. The normal Fe response is subtracted with the use of M-H loops taken above Tc and the remaining magnetization suppression of the MgB2 is described in terms of field shunting in the Fe "shield". The level of Fe shielding, both of regions outside of the sample from the MgB2, as well as the MgB2 from the outside is …
Effect Of Addition Of Tio2/Sio2 Nanoparticles On Hc2 And Hirr In Mgb2 Bulks, Y. Zhang, Saeid Soltanian, Y. Zhao, S. Zhou, S. X. Dou
Effect Of Addition Of Tio2/Sio2 Nanoparticles On Hc2 And Hirr In Mgb2 Bulks, Y. Zhang, Saeid Soltanian, Y. Zhao, S. Zhou, S. X. Dou
Shi Xue Dou
In this paper, MgB2 bulks were prepared with doped TiO2 nanoparticles surface-modified by 5-10% SiO2. Quantitative X-ray diffraction (XRD) analysis was performed to obtain the weight fraction of impurities using the Rietveld method. The effects of addition of TiO2/SiO2 nanoparticles on the critical temperature (Tc), the upper critical field (Hc2), and the irreversibility field (Hirr) as a function of doping rates at 750°C are reported. It has been found that the addition of TiO2/SiO2 nanoparticles resulted in small depressions in Tc, while the Hc2 and Hirr performances were improved due to TiO2/SiO2 nanoparticle doping.
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Shi Xue Dou
Direct comparison of the magnetic and transport critical current density (Jc) for the same pieces of copper-sheathed MgB2 wires shows a large discrepancy in magnitude and field dependence of the two. The value of magnetic Jc can differ from the value of transport Jc by a factor of 10 or more. This discrepancy does not occur merely because of the difference in the voltage at which the magnetic and transport Jc are measured, but mainly because of the specific microstructure of MgB2. Such microstructure results in superconducting screening on at least two different length-scales, despite the absence of weak links …